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Abstract:

A water-insoluble liquid crystalline gel composed mainly of a
water-soluble polymer, itself having a gelation function together with a
liquid crystal formation function and having an optical property is
produced.
First, the water-soluble polymer is dissolved in water or an aqueous
solution containing a salt(s) to prepare a polymer solution.
Subsequently, this polymer solution is dialyzed in an aqueous solution
containing a chemical crosslinking agent, thereby obtaining the gel
having a liquid crystal structure and composed mainly of the
water-soluble polymer. Said water soluble polymer is one or two or more
polymers selected from the group consisting of water-soluble biopolymers,
derivatives of these water-soluble biopolymers and water-soluble
synthesized polymers. The water-soluble biopolymers are one or two or
more polymers selected from the group consisting of nucleic acids,
polysaccharides, proteins, modified proteins and polyamino acids. The
water-soluble synthesized polymers are one or two or more polymers
selected from the group consisting of polyvinyl alcohol, polyethylene
glycol, polyacrylic acid and polystyrene sulfonic acid.

Claims:

1. (canceled)

2. (canceled)

3. (canceled)

4. (canceled)

5. (canceled)

6. A process for producing a gel comprising a step of dissolving a
water-soluble polymer in water or an aqueous solution containing a
salt(s) to prepare a water-soluble polymer solution and a step of
dialyzing said polymer solution in an aqueous solution containing a
chemical crosslinking agent, thereby obtaining the gel composed mainly of
the water-soluble polymer and having a liquid crystal structure;wherein
said water-soluble polymer is one or two or more polymers selected from
the group consisting of water-soluble biopolymers, derivatives of these
water-soluble biopolymers and water-soluble synthesized polymers, and
said water-soluble biopolymers are one or two or more polymers selected
from the group consisting of nucleic acids, polysaccharides, proteins,
modified proteins and polyamino acids, and said water-soluble synthesized
polymers are one or two or more polymers selected from the group
consisting of polyvinyl alcohol, polyethylene glycol, polyacrylic acid
and polystyrene sulfonic acid;wherein said chemical crosslinking agent is
one or two or more selected from the group consisting of formaldehyde,
glutaraldehyde, ethylene glycol diglycidyl ether and epichlorohydrin;and
wherein the step of obtaining said gel having the liquid crystal
structure comprises a step of filling and sealing the polymer solution in
a dialysis tube composed of a semipermeable membrane, a step of forming a
cylindrical gel having a concentric multilayered structure when a cross
section perpendicular to a longitudinal direction of the tube is
observed, in the tube, by repeating transferring the tube together with
the above aqueous solution to a second incubator in which the temperature
is kept lower than in a first incubator and dialyzing the polymer
solution in the tube in the second incubator and further transferring
again the tube together with the above aqueous solution to the first
incubator and dialyzing the polymer solution in the tube in the first
incubator, after immersing the tube in which the polymer solution has
been filled in the aqueous solution containing the chemical crosslinking
agent to dialyze the polymer solution in the tube in the first incubator
kept at a predetermined temperature and subsequently, and a step of
obtaining a solid-core columnar or hollow-core cylindrical gel by taking
out the above gel from the tube and rinsing the gel with the water.

7. (canceled)

8. (canceled)

9. A process for producing a gel comprising a step of dissolving a
water-soluble polymer in water or an aqueous solution containing a
salt(s) to prepare a water-soluble polymer solution and a step of
dialyzing said polymer solution in an aqueous solution containing a
chemical crosslinking agent, thereby obtaining the gel composed mainly of
the water-soluble polymer and having a liquid crystal structure;wherein
said water-soluble polymer is one or two or more polymers selected from
the group consisting of water-soluble biopolymers, derivatives of these
water-soluble biopolymers and water-soluble synthesized polymers, and
said water-soluble biopolymers are one or two or more polymers selected
from the group consisting of nucleic acids, polysaccharides, proteins,
modified proteins and polyamino acids, and said water-soluble synthesized
polymers are one or two or more polymers selected from the group
consisting of polyvinyl alcohol, polyethylene glycol, polyacrylic acid
and polystyrene sulfonic acid;wherein said chemical crosslinking agent is
one or two or more selected from the group consisting of formaldehyde,
glutaraldehyde, ethylene glycol diglycidyl ether and epichlorohydrin;and
wherein the step of obtaining said gel having the liquid crystal
structure comprises a step of forming a spherical gel by dropping the
polymer solution into the aqueous solution containing the chemical
crosslinking agent using a syringe, a nozzle or a micropipette to form a
semipermeable membrane on all circumferences of a droplet in a first
incubator kept at a predetermined temperature, and a step of forming a
spherical gel having a concentric multilayered structure when a diameter
cross section is observed, by repeating transferring said spherical gel
together with said aqueous solution to a second incubator in which the
temperature is kept lower than in a first incubator to dialyze the
polymer solution in said spherical gel in said second incubator and
subsequently transferring again said spherical gel together with said
aqueous solution to said first incubator to dialyze the polymer solution
in said spherical gel in said first incubator.

10. (canceled)

11. (canceled)

12. A process for producing a gel comprising a step of dissolving a
water-soluble polymer in water or an aqueous solution containing a
salt(s) to prepare a water-soluble polymer solution and a step of
dialyzing said polymer solution in an aqueous solution containing a
chemical crosslinking agent, thereby obtaining the gel composed mainly of
the water-soluble polymer and having a liquid crystal structure;wherein
said water-soluble polymer is one or two or more polymers selected from
the group consisting of water-soluble biopolymers, derivatives of these
water-soluble biopolymers and water-soluble synthesized polymers, and
said water-soluble biopolymers are one or two or more polymers selected
from the group consisting of nucleic acids, polysaccharides, proteins,
modified proteins and polyamino acids, and said water-soluble synthesized
polymers are one or two or more polymers selected from the group
consisting of polyvinyl alcohol, polyethylene glycol, polyacrylic acid
and polystyrene sulfonic acid;wherein said chemical crosslinking agent is
one or two or more selected from the group consisting of formaldehyde,
glutaraldehyde, ethylene glycol diglycidyl ether and epichlorohydrin;and
wherein the step of obtaining said gel having the liquid crystal
structure comprises a step of dropping said polymer solution on a first
flat plate and then flattening the dropped polymer solution by being
covered with another second flat plate, a step of forming a platy or
film-like gel between said first and second flat plates, having a
concentric multilayered structure wherein the polymer is radially
oriented from the center in each layer when a plate surface or a film
surface is observed, by repeating transferring said platy or film-like
gel together with said aqueous solution to a second incubator in which
the temperature is kept lower than in a first incubator to dialyze the
polymer solution in said platy or film-like gel in said second incubator
and further transferring again said platy or film-like gel together with
said aqueous solution to said first incubator to dialyze the polymer
solution in said platy or film-like gel in said first incubator, after
forming the platy or film-like gel by immersing the polymer solution
sandwiched with said first and second flat plates in the aqueous solution
containing said chemical crossing agent to form a semipermeable membrane
on a part of said polymer solution not covered with said first and second
flat plates in the first incubator kept at a predetermined temperature,
and a step of obtaining the platy or film-like gel by taking out said gel
from said first and second flat plates and rinsing the gel with the
water.

13. (canceled)

14. (canceled)

15. A process for producing a gel comprising a step of dissolving a
water-soluble polymer in water or an aqueous solution containing a
salt(s) to prepare a water-soluble polymer solution and a step of
dialyzing said polymer solution in an aqueous solution containing a
chemical crosslinking agent, thereby obtaining the gel composed mainly of
the water-soluble polymer and having a liquid crystal structure;wherein
said water-soluble polymer is one or two or more polymers selected from
the group consisting of water-soluble biopolymers, derivatives of these
water-soluble biopolymers and water-soluble synthesized polymers, and
said water-soluble biopolymers are one or two or more polymers selected
from the group consisting of nucleic acids, polysaccharides, proteins,
modified proteins and polyamino acids, and said water-soluble synthesized
polymers are one or two or more polymers selected from the group
consisting of polyvinyl alcohol, polyethylene glycol, polyacrylic acid
and polystyrene sulfonic acid;wherein said chemical crosslinking agent is
one or two or more selected from the group consisting of formaldehyde,
glutaraldehyde, ethylene glycol diglycidyl ether and epichlorohydrin;and
wherein the step of obtaining said gel having the liquid crystal
structure comprises a step of forming a rod-like or fibrous gel by
pushing out said polymer solution into the aqueous solution containing
the chemical crosslinking agent using a syringe or a nozzle to form a
semipermeable membrane on all circumferences of a rod-like or fibrous
body in a first incubator kept at a predetermined temperature, a step of
forming a rod-like or fibrous gel having a concentric multilayered
structure when a cross section perpendicular to a longitudinal direction
is observed, by repeating transferring said rod-like or fibrous gel
together with said aqueous solution to a second incubator in which the
temperature is kept lower than in a first incubator to dialyze the
polymer solution in said rod-like or fibrous gel in said second incubator
and subsequently transferring again said rod-like or fibrous gel together
with said aqueous solution to said first incubator to dialyze the polymer
solution in said rod-like or fibrous gel in said first incubator, and a
step of obtaining a solid-core or hollow rod-like or fibrous gel by
taking out said gel from said aqueous solution and rinsing the gel with
the water.

16. The process for producing the gel according to any one claims 6, 9, 12
or 15 wherein a concentration of the chemical crosslinking agent in the
aqueous solution containing the chemical crosslinking agent is 0.1% by
weight or higher and the concentration equal to or lower than its
saturation concentration.

17. (canceled)

18. A gel produced by the process according to any one of claims 6, 9, 12,
15 or 16 having a cylindrical, spherical, platy, film-like, rod-like or
fibrous liquid crystal structure composed of a water-soluble polymer.

19. (canceled)

20. The gel having the liquid crystal structure according to claim 18
wherein when the gel includes a protein, said protein is myosin, gelatin
or collagen, the polysaccharide is curdlan or chitosan and the nucleic
acid is DNA or RNA.

21. The gel having the liquid crystal structure according to claim 18,
which is formed into a cylindrical, rod-like or fibrous shape, wherein
the polymer is radially oriented from the center when a cross section
perpendicular to a longitudinal direction is observed.

22. The gel having the liquid crystal structure according to claim 21
having a concentric multilayered structure when a cross section
perpendicular to the longitudinal direction is observed.

23. The gel having the liquid crystal structure according to claim 18
which is formed into a spherical shape, wherein the polymer is radially
oriented from the center when a diameter cross section is observed.

24. The gel having the liquid crystal structure according to claim 23
having a concentric multilayered structure when the diameter cross
section is observed.

25. The gel having the liquid crystal structure according to claim 18,
which is formed into a platy or film-like shape, wherein the polymer is
radially oriented from the center when a plate surface or a film surface
is observed.

26. The gel having the liquid crystal structure according to claim 25
having a concentric multilayered structure when a plate surface or a film
surface is observed.

27. The process for producing the gel according to any one of claims 6, 9,
12 or 15 wherein when the gel includes a protein, said protein is myosin,
gelatin or collagen, the polysaccharide is curdlan or chitosan and the
nucleic acid is DNA or RNA.

Description:

TECHNICAL FIELD

[0001]The present invention relates to a process for producing a gel with
a liquid crystal structure (hereinafter referred to as a "liquid
crystalline gel") by dialyzing or immersing various polymer solutions in
an aqueous solution of a chemical crosslinking agent, and the liquid
crystalline gel produced by this process.

BACKGROUND ART

[0002]It is well-known that DNA (deoxyribonucleic acid) has a double helix
structure. DNA in aqueous solution is classified into an electrolyte
polymer with a continuous length of about 500 angstroms having a negative
charge every about 1.5 angstroms. It is also known that a base pair layer
and a major groove in the double helix structure of DNA have a selective
absorptivity of an aromatic compound having a planer chemical structure.

[0003]Conventionally, the process has been disclosed in which a
water-insoluble crosslinked polymer of the water-soluble DNA is
immobilized on a support by irradiating ultraviolet light with a
wavelength of 250 to 270 nm to an aqueous solution of the water-soluble
DNA (e.g., DNA derived from salmon sperm) or a liquid film thereof on the
support, or a thin layer of the water-soluble DNA on the support, or a
thin layer obtained by concentrating or drying the liquid film of the
water-soluble DNA on the support (e.g., see Patent Document 1). According
to this process, the ultraviolet light causes a crosslinking reaction of
the DNA derived from the salmon sperm to insolubilize in water, and a
carcinogenic substance and an endocrine disturbing chemical composed of
the aromatic compound having the planer chemical structure can be
absorbed by this insolubilization technology.

[0004]Meanwhile, the present applicant applied the process for producing a
liquid crystalline gel by dialyzing the solution of the polymer such as
curdlan and DNA in the aqueous solution of a metal cation for a patent
(see Japanese Patent Application 2004-249638, International Patent
Application PCT/JP2005/015395). Among these liquid crystalline gels
produced by the dialysis, in particular, the liquid crystalline gel
composed of the curdlan is expected to be practically applied to optical
parts and drug carriers because of its characteristic liquid crystal
structure. The liquid crystalline gel composed of DNA is expected to be
practically applied to environmental purification materials by taking
advantage of its absorbable function of environmental pollutants.

[0005]Patent Document 1: JP 2001-81098-A (Claims, [0019], [0022])

DISCLOSURE OF INVENTION

Problem to be Solved by the Invention

[0006]However, in the process for producing the water-insoluble DNA
crosslinked body by ultraviolet light irradiation, described in the above
conventional patent Document 1, since the DNA is crosslinked using the
ultraviolet light, it is necessary to irradiate the ultraviolet light to
the DNA for a long time. Thus, the process is not suitable for a mass
production. This process cannot produce the liquid crystalline gel so
that the polymer itself having the optical property has a gelation
function together with a liquid crystal formation function like in the
present invention.

[0007]In the above process for producing the liquid crystalline gel
applied by the present applicant, the gel is conceivable to be a physical
gel attributed to physical bonds such as a coulomb force and a hydrogen
bond between a metal ion and the polymer. Thus, if the gel is kept in
water for a long time, it is likely that physical properties such as
elastic modulus and birefringence are reduced by elution of the metal
ion.

[0008]A first object of the present invention is to provide a process for
producing a water-insoluble liquid crystalline gel composed mainly of
various water-soluble polymers, which itself has the gelation function
together with the liquid crystal formation function and has the optical
property, and the liquid crystalline gel.

[0009]A second object of the present invention is to provide a process for
producing a liquid crystalline gel capable of obtaining relatively stable
liquid crystal physical property and dynamic property for an external
environment by dialyzing or immersing a polymer solution in an aqueous
solution containing a chemical crosslinking agent, and the liquid
crystalline gel.

[0010]A third object of the present invention is to provide a process for
producing a liquid crystalline gel, in which a liquid crystalline
gelation of the polymer using the chemical crosslinking agent, which has
been impossible by the conventional art, is made possible, and the liquid
crystalline gel composed mainly of the water-soluble polymer can be
produced inexpensively and massively, and the liquid crystalline gel.

Means for Solving Problem

[0011]The invention according to claim 1 is a process for producing a
liquid crystalline gel comprising a step of dissolving a water-soluble
polymer in water or an aqueous solution containing a salt(s) to prepare a
water-soluble polymer solution, and a step of dialyzing this polymer
solution in an aqueous solution containing a chemical crosslinking agent,
thereby obtaining the gel composed mainly of the water-soluble polymer
and having a liquid crystal structure.

[0012]The "liquid crystalline gel" in the present invention refers to
those where the water-soluble polymer in an aggregation state is the
liquid crystal and simultaneously the gel.

[0013]The invention according to claim 18 is the gel produced by the
process according to any one of claims 1 to 17, composed of the
water-soluble polymer and having the liquid crystal structure which is
columnar, cylindrical, spherical, platy, film-shaped, rod-like or
fibrous.

Effect of the Invention

[0014]In the process for producing the liquid crystalline gel according to
claim 1 of the present invention, the liquid crystalline gel which is
columnar, cylindrical, spherical, platy, film-shaped, rod-like or fibrous
is formed by dissolving the water-soluble polymer in water or the aqueous
solution containing the salt(s) to prepare the water-soluble polymer
solution and dialyzing this polymer solution in the aqueous solution
containing the chemical crosslinking agent. This liquid crystal is
insoluble in water, and is characterized in that the polymer itself has
the gelation function together with the liquid crystal formation
function.

[0015]The dynamic property and the optical property in the above liquid
crystalline gel can be controlled by changing a concentration of the
salt(s), the concentration of the water-soluble polymer and the
concentration of the chemical crosslinking agent upon the production. The
water-insoluble liquid crystalline gel is obtained by a simple
manipulation that the polymer solution is dialyzed in the aqueous
solution containing the chemical crosslinking agent. This process is
suitable for the mass production as well as can be practically applied to
liquid crystalline gelation technology of broad polymers.

[0016]The liquid crystalline gel composed mainly of the water-soluble
polymer according to claim 18 of the present invention is formed into a
columnar, cylindrical, spherical, platy, film-shaped, rod-like or fibrous
shape. When the gel is observed in a cross section perpendicular to a
longitudinal direction, a diameter cross section or a plate surface or a
film surface, the polymer is radially oriented from the center. First,
since this liquid crystalline gel is a chemical gel prepared by a
chemical reaction, it is possible to prevent the reduction of the
mechanical property and the optical property, which has been concerned in
the conventional liquid crystalline gels. Second, in this liquid
crystalline gel, it is possible to more effectively control the
mechanical property and the optical property by changing a solvent,
compared with the liquid crystalline gels prepared by the conventional
art. Third, it is possible to make various materials the liquid
crystalline gels by designing the polymer or the chemical crosslinking
agent suitable for making the liquid crystalline gel.

[0017]The liquid crystalline gel of the present invention is the
covalently bound gel whereas the liquid crystalline gel already applied
by the present applicant, i.e., the liquid crystalline gel produced by
dialyzing the solution of the polymer such as curdlan and DNA in the
aqueous solution of the metal cation is the ionically bound gel. Thus, in
the liquid crystalline gel of the present invention, the range of the
polymer which can produce the liquid crystalline gel is expanded as well
as the liquid crystalline gel which is tough and withstands a harsh
condition can be produced.

BRIEF DESCRIPTION OF DRAWINGS

[0018]FIG. 1 is a sectional schematic view showing a molecular structure
of a solid-core cylindrical liquid crystalline gel in an embodiment of
the present invention;

[0019]FIG. 2 is a view obtained by observing the liquid crystal in FIG. 1
under crossed nicols;

[0020]FIG. 3 is a graph showing changes of a birefringent index Dn by
distance from the center of a liquid film, which is one of optical
properties in the liquid crystalline gels in Examples 3, 7 and 11;

[0021]FIG. 4 is a graph showing changes of the birefringent index Dn by
distance from the center of the liquid film, which is one of optical
properties in the liquid crystalline gels in Examples 4, 8 and 12;

[0022]FIG. 5 is a constitution view of a birefringence measurement
apparatus for measuring the birefringent index Δn in the liquid
crystalline gel;

[0023]FIG. 6 is a view showing stress-strain curves of thin films of the
liquid crystalline gels in Example 15 and Comparative Example 21
immediately after making the liquid crystalline gel;

[0024]FIG. 7 is a view showing the stress-strain curves of the thin films
of the liquid crystalline gels in Example 16 and Comparative Example 22
after warming the thin films of the liquid crystalline gels in Example 15
and Comparative Example 21 at 40° C. for half a day;

[0025]FIG. 8 is a view showing the stress-strain curves of the thin films
of the liquid crystalline gels in Example 15 immediately after making the
liquid crystalline gel and thin films of the liquid crystalline gels in
Example 16 after warming the liquid crystalline gel;

[0026]FIG. 9 is a view showing the stress-strain curves of the thin films
of the liquid crystalline gels in Comparative Example 21 immediately
after making the liquid crystalline gel and thin films of the liquid
crystalline gels in Comparative Example 22 after warming the liquid
crystalline gel;

[0027]FIG. 10 is a view obtained by observing the liquid crystal gel in
Example 17 under crossed nicols;

[0028]FIG. 11 is a view obtained by observing the liquid crystalline gels
in Examples 19 to 21 and Comparative Example 9 before and after solvent
replacement under natural light and crossed nicols;

[0029]FIG. 12 is a graph showing the comparison of the birefringence
Δn in the liquid crystalline gels in Examples 19 to 21 before and
after the solvent replacement;

[0030]FIG. 13 is a graph showing the comparison of Young's modulus in the
liquid crystalline gels in Examples 19 to 21 before and after the solvent
replacement; and

[0031]FIG. 14 is a view obtained by observing the liquid crystalline gels
of Example 22 and Comparative Example 10 under crossed nicols.

BEST MODES FOR CARRYING OUT THE INVENTION

[0032]Best modes for carrying out the present invention will be described
below.

[0033]A major ingredient of the liquid crystalline gel of the present
invention is one or two or more polymers selected from the group
consisting of water-soluble biopolymers, derivatives of these biopolymers
and water-soluble polymers. The water-soluble polymer contained in the
liquid crystalline gel includes one or more polymers selected from the
group consisting of nucleic acids, polysaccharides, proteins, modified
proteins and polyamino acids, or derivatives thereof or combinations
thereof. The nucleic acids include DNA, RNA (ribonucleic acid) or
combinations of DNA and RNA. Examples of polysaccharides include chitin
and chitosan, which are major ingredients of outer shells in shellfishes,
curdlans that are fermented polysaccharides produced by microorganisms,
and schizophylan produced by Schizophyllum. Examples of the derivatives
of polysaccharides include methylcellulose, hydroxypropylcellulose,
hydroxypropylmethylcellulose and carboxymethylcellulose. Examples of the
protein include collagen and myosin. Examples of the modified protein
include gelatin. Examples of the polyamino acid include polyglutamic acid
and polylysine. Furthermore, examples of the water-soluble synthesized
polymer include one or two or more polymers selected from the group
consisting of polyethylene glycol, polyethylene oxide, polyvinyl alcohol
polyvinylmethyl alcohol, polyvinyl pyrrolidone, polyacrylic acid and
polystyrene sulfonic acid. By controlling the molecular weight of these
polymers, it is possible to optimize a prepared product to be suitable
for its use.

[0034]In a weight ratio of the combination in the liquid crystalline gel,
when the amount of a rod-like or semi-flexible water-soluble polymer
which is the major ingredient is 100% by weight, the amount of a rod-like
polymer which is a minor ingredient is 1 to 400% by weight and preferably
1 to 100% by weight, and the amount of a semi-flexible polymer which is
the minor ingredient is 1 to 150% by weight and preferably 1 to 100% by
weight. Here, the amount of the rod-like polymer is limited to the range
of 1 to 400% by weight because if the amount is less than a lower limit
value, the effect obtained by combining two or more water-soluble
polymers is reduced and if the amount exceeds an upper limit value,
aggregations are formed between the water-soluble polymer which is the
major ingredient in the liquid crystalline gel and the rod-like polymer
combined with this water-soluble polymer and the aggregations are
precipitated. The amount of the semi-flexible polymer is limited to the
range of 1 to 400% by weight because if the amount is less than the lower
limit value, the effect obtained by combining two or more water-soluble
polymers is reduced and if the amount exceeds the upper limit value, the
aggregations are formed between the water-soluble polymer which is the
major ingredient in the liquid crystalline gel and the semi-flexible
polymer combined with this water-soluble polymer and the aggregations are
precipitated, or an orientation of the water-soluble polymer which is the
major ingredient in the liquid crystalline gel is prevented.

[0035]A shape of the liquid crystalline gel is columnar, cylindrical, bar,
fibrous, spherical, platy or film-like, and the form of the liquid
crystalline gel has a three dimensional structure. When the liquid
crystalline gel is formed into the columnar, cylindrical, rod-like or
fibrous shape, observing in a cross section perpendicular to the
longitudinal direction, the water-soluble polymer oriented radially from
the center is the major ingredient. This liquid crystalline gel includes
the gel having a concentric multilayered structure when observed in a
cross section perpendicular to the longitudinal direction. When the
liquid crystalline gel is formed into a spherical shape, the
water-soluble polymer oriented radially from the center when the gel is
observed in a diameter cross section is the major ingredient in the
liquid crystalline gel. This liquid crystalline gel also includes the gel
having the concentric multilayered structure when observed in a diameter
cross section. Furthermore when the liquid crystal is formed into a platy
or film-like shape, the water-soluble polymer oriented radially from the
center when a plate surface or a film surface is observed is the major
ingredient in the liquid crystalline gel. This liquid crystalline gel
also includes the gel having the concentric multilayered structure when
the plate surface or film surface is observed. Basically, the liquid
crystalline gel composed mainly of these water-soluble polymers is
obtained by dissolving the water-soluble polymer in water or the aqueous
solution of the salt(s) to prepare the polymer solution and subsequently
dialyzing this polymer solution in the aqueous solution containing the
chemical crosslinking agent.

[0036]Representatively, gelatin having the molecular weight of 300,000 is
used as the water-soluble polymer, water is used as the solvent to
dissolve this, and the process will be described.

[0037]First, gelatin is dissolved in water to prepare a gelatin solution.
In order to produce the liquid crystalline gel of the present invention,
gelatin at 5 to 30% by weight, preferably 20 to 30% by weight based on
the water is added to the water. When the amount of added gelatin is less
than the lower limit value, no liquid crystalline gel is formed. When it
exceeds the upper limit value, the viscosity increases and it becomes
difficult to obtain the homogenous solution. Then, the resulting gelatin
solution is heated to 40° C. to solate and filled in a dialysis
tube composed of a semipermeable membrane. Before filling, a lower end of
the tube is sealed. The semipermeable membrane is not particularly
limited, but it is necessary to choose a material, which is not dissolved
with the chemical crosslinking agent. Acetate cellulose and polymethyl
methacrylate are exemplified, and a cellulose-based dialysis tube is
preferable. Here, a speed of the gelation and a crystallinity and a layer
structure of the resulting liquid crystalline gel are changed by a
membrane thickness and the diameter of the dialysis tube. An outer
diameter of the cylindrical liquid crystalline gel obtained finally
depends on the diameter of the tube. The diameter and the length of the
tube are determined depending on the use of the liquid crystalline gel.
For example, the diameter is selected from the range of 6 mm to 10 cm,
and the cylindrical or columnar liquid crystalline gel having the outer
diameter of 6 mm to 10 cm and an inner diameter of 0 mm to 4 cm
(thickness: 1.8 mm to 3 cm) is obtained from this tube. The gelatin
solution is filled and sealed in the tube by filling the gelatin solution
in the tube and sealing an upper end of the tube.

[0038]Then, the gelatin solution filled and sealed in the tube is stored
in a cold place (4° C.) to gelate physically for an appropriate
time period. Subsequently, the gelatin solution filled and sealed in the
tube is immersed in the aqueous solution containing the chemical
crosslinking agent (glutaraldehyde, ethylene glycol diglycidyl ether).
After the immersion, the chemical crosslinking agent is diffused in the
tube to chemically gelate the gelatin solution, and further in this
process, the liquid crystallization occurs. As the chemical crosslinking
agent at that time, formaldehyde, glutaraldehyde or ethylene glycol
diglycidyl ether is suitable in that gelatin is chemically crosslinked.
The concentration of the chemical crosslinking agent in the aqueous
solution containing the chemical crosslinking agent is preferably 0.1% by
weight or higher and the concentration equal to or lower than a saturated
concentration, and more preferably within the range of 20 to 40% by
weight. When the concentration of the chemical crosslinking agent in the
aqueous solution containing the chemical crosslinking agent is lower than
the lower limit value, the gel is not formed. When it exceeds the upper
limit value, the strain of the liquid crystalline gel occurs due to
remarkable shrinkage of the gel. A temperature of this aqueous solution
is preferably 0C or above and the temperature equal to or lower than a
sol-gel transition temperature of gelatin, and more preferably within the
range of 0 to 20° C. When the temperature of the above aqueous
solution is lower than the lower limit value, a diffusion speed of the
chemical crosslinking agent is slow and the solution is likely to be
solidified. When it exceeds the upper limit value, the liquid crystalline
gelation does not occur, or the function is reduced, e.g., an orientation
degree is reduced. By the above dialysis, a columnar body having the
diameter corresponding to the diameter of this tube is formed in the
tube. Generally when a dialysis time period is shortened, the center of
the columnar body is the sol and the circumference thereof is the liquid
crystalline gel. Conversely when the dialysis time period is prolonged,
or when the gelatin concentration is increased or the concentration of
the chemical crosslinking agent in the aqueous solution containing the
chemical crosslinking agent is increased, the solid-core columnar liquid
crystalline gel is formed. That is, when the center of the columnar body
is the sol, a sol part is eliminated by taking out this columnar body
from the tube and then rinsing it with water, and the cylindrical liquid
crystalline gel is obtained. When the entire columnar body is the gel, by
taking out this columnar body from the tube and then rinsing it with
water, the solid-core columnar liquid crystalline gel is formed. For
example, under the condition where the diameter of the dialysis tube is
12 mm, the gelatin concentration is 30% by weight and the concentration
of glutaraldehyde is 25% by weight, when the dialysis time period is 0 to
240 minutes, the cylindrical liquid crystalline gel is formed, and when
the dialysis time period is 240 minutes or longer, the columnar liquid
crystalline gel is formed.

[0039]When the cylindrical liquid crystalline gel is cut perpendicularly
to the longitudinal direction and a cut surface is observed under the
natural light, the polymer is radially oriented in concentric circle from
the center like a cross section of a pineapple fruit as shown in a
schematic view in FIG. 1. Meanwhile, when it observed under crossed
nicols, cross lines appear as shown in FIG. 2, proving that this gel has
the liquid crystal structure. These cross lines indicate that gelatin
molecules or aggregates thereof are regularly oriented from the center.

[0040]In order to make the concentric multilayered structure when the
cylindrical or columnar liquid crystalline gel is observed at its cross
section perpendicular to the longitudinal direction, the following
process is performed. First, the gelatin solution is filled in the tube
to form the columnar body. Then, this columnar body is placed at a
predetermined temperature (e.g., 40° C.) in the range of 10 to
50° C., e.g., in a first incubator, and immersed in the aqueous
solution containing the chemical crosslinking agent for 10 to 20 minutes
to dialyze the gelatin solution in the above tube. Specifically, the
aqueous solution containing the chemical crosslinking agent is retained
in a container, the columnar body is immersed in this aqueous solution
containing the chemical crosslinking agent, the whole container is placed
in the first incubator and the gelatin solution in the columnar body is
dialyzed. Subsequently, the whole container including the above columnar
body together with the aqueous solution containing the chemical
crosslinking agent is transferred from the first incubator into a second
incubator in which the temperature is kept at 5 to 40° C.,
preferably 10 to 40° C. lower than in the first incubator. The
gelatin solution in the columnar body is dialyzed in this second
incubator for 10 to 20 minutes. Further, the whole container including
the above columnar body together with the aqueous solution containing the
chemical crosslinking agent is transferred again to the first incubator.
The gelatin solution in the columnar body is dialyzed in the first
incubator for 10 to 20 minutes. This way, by repeating the dialysis of
the columnar body under the conditions at different temperature, it is
possible to form the cylindrical or columnar liquid crystalline gel
having the concentric multilayered structure when a cross section
perpendicular to the longitudinal direction is observed, in the tube. A
thermal medium retained in the above first and second incubator may be a
liquid or a gas, but the water is preferable. Here, the temperature of
the thermal medium in the first incubator is limited within the range of
10 to 50° C. because when the temperature is lower than 10°
C., it becomes difficult to set the temperature in the second incubator
and when the temperature is higher than 50° C., the biopolymers
such as proteins are denatured and the chemical crosslinking agent is
excessively vaporized. The temperature of the thermal medium in the
second incubator is 5 to 40° C. lower than the temperature of the
thermal medium in the first incubator because when the temperature is
lower than 5° C., no clear multilayer structure is obtained and
when the temperature is higher than 40° C., the solution is likely
to be frozen. By repeating a step of immersing the tube in the aqueous
solution containing the chemical crosslinking agent at a predetermined
temperature, a step of taking out the tube from this aqueous solution and
leaving it stand in air for 5 to 30 minutes and immersing this tube in
the above aqueous solution again, the cylindrical gel having the
concentric multilayered structure when a cross section perpendicular to
the longitudinal direction of the tube is observed may be formed in the
tube.

[0041]As is the case with the first process, representatively, gelatin is
used as the water-soluble polymer, the water is used as the solvent in
which this is dissolved, and the process will be described.

[0042]First, gelatin is dissolved in the water to prepare the gelatin
solution. Gelatin is added to the water in order to produce the liquid
crystalline gel of the present invention. This process is different from
the first process in that the concentration of gelatin in the gelatin
solution when the gelatin solution is prepared requires the viscosity to
an extent that the spherical shape can be kept by surface tension during
the formation of the semipermeable membrane in order to self-form the
semipermeable membrane.

[0043]In the second process, a syringe, a nozzle, a spray or a
micropipette is used in place of the dialysis tube composed of the
semipermeable membrane. The outer diameter of the spherical liquid
crystalline gel finally obtained depends on a nozzle size of an outlet in
the syringe. The nozzle size of the outlet in the syringe is determined
depending on the use of the liquid crystalline gel, and selected from the
range of 1 μm to 1 mm. The spherical liquid crystalline gel having the
outer diameter of 100 μm to 4 mm is obtained from this syringe. After
filling the gelatin solution in the syringe, the syringe with pointing
the outlet down is secured at a predetermined position 1 to 15 cm upper
than a liquid surface of the aqueous solution containing the chemical
crosslinking agent.

[0044]Then, the gelatin solution filled in the syringe is dropped into the
aqueous solution containing the chemical crosslinking agent by applying
the pressure inside the syringe. At that time, it is preferable that the
temperature of the aqueous solution containing the chemical crosslinking
agent is kept at low temperature of 4 to 10° C. The semipermeable
membrane is formed on all circumferences of a droplet while suspending
the gelatin solution droplets in the aqueous solution. By keeping this
state, the gelatin solution, which composes the droplet, is dialyzed and
the spherical liquid crystalline gel is formed. The liquid crystalline
gel having the outer diameter depending on the nozzle size of the outlet
in the syringe is formed.

[0045]When this spherical liquid crystalline gel is cut in a diameter
direction to make hemispheres and the cut surface is observed, although
not shown in the figure, the spherical liquid crystalline gel has an
outer shell and is in concentric circle, and the polymer such as gelatin
is radially oriented from the center. Inside this liquid crystalline gel,
the center portion is not gelated and the sol portion is present in some
cases. The mechanism to form this structure is the same as in the
cylindrical liquid crystalline gel.

[0046]In order to make the concentric multilayered structure when the
spherical liquid crystalline gel is observed in its diameter cross
section, the following process is performed. First, the spherical gel is
prepared by dropping and immersing for 1 to 5 minutes the gelatin
solution in the aqueous solution containing the chemical crosslinking
agent in the first incubator kept at a predetermined temperature (e.g.,
40° C.) in the range of 10 to 50° C. Specifically, the
spherical gel is prepared by dropping and immersing the gelatin solution
in the aqueous solution containing the chemical crosslinking agent in the
container, in the state where the container in which the aqueous solution
containing the chemical crosslinking agent is retained is placed in the
first incubator. Then, the whole container including the spherical gel
together with the aqueous solution containing the chemical crosslinking
agent is transferred from the first incubator into the second incubator
in which the temperature is kept at 5 to 40° C., preferably 10 to
20° C. (e.g., 40° C.) lower than in the first incubator,
and the gelatin solution in the spherical gel is dialyzed for 1 to 5
minutes. Further, the whole container including the spherical gel
together with the aqueous solution containing the chemical crosslinking
agent is transferred again into the first incubator, and the gelatin
solution in the spherical gel is dialyzed for 1 to 5 minutes in the first
incubator. This way, by repeating the dialysis of the spherical gel under
the conditions at different temperature, it is possible to form the
spherical liquid crystalline gel having the concentric multilayered
structure when a diameter cross section is observed. When the drug is
contained in this gel or in a sol layer inside the gel and the gel is put
in the body, it is possible to gradually release the drug in the body.
That is, when the drug contained in an outmost layer of the gel or the
sol layer inside the gel is released, the drug contained in a second
outmost layer migrates in the outmost layer and is released from the
outmost layer in the body. The drug put in the body is gradually released
by migrating the drug from an inner layer to the outmost layer. By
repeating the step of immersing the spherical liquid crystalline gel in
the aqueous solution containing the chemical crosslinking agent at a
predetermined temperature, the step of taking out the spherical liquid
crystalline gel from this aqueous solution and leaving it stand in air
for 5 to 30 minutes and the step of immersing this spherical liquid
crystalline gel in the above aqueous solution again, the spherical liquid
crystalline gel having the concentric multilayered structure when the
spherical liquid crystalline gel is observed in its diameter cross
section may be formed.

[0047]First, gelatin having the molecular weight of 300,000 is dissolved
in the water to prepare the gelatin solution where the gelatin
concentration is 20% by weight. This gelatin solution is warmed at
40° C. to solate, subsequently the sol is aspirated by a
capillary, and is gelated thoroughly in a cool place. Subsequently, the
gelatin gel is pushed out from the capillary in the aqueous solution
containing glutaraldehyde at 25% by weight. This forms the gel having the
rod-like or fibrous crystal structure, which is in concentric circle and
where the polymer is radially oriented from the center when a cross
section perpendicular to the longitudinal direction.

[0048]In order to make the concentric multilayered structure in the
rod-like or fibrous liquid crystalline gel when a cross section
perpendicular to the longitudinal direction is observed, the following
process is performed. First, the rod-like or fibrous liquid crystalline
gel is prepared by for 0.1 to 5 minutes immersing the rod-like or fibrous
droplet obtained by pushing out the gelatin solution using the nozzle,
the syringe needle or the micropipette in the aqueous solution containing
the chemical crosslinking agent, in the first incubator kept at a
predetermined temperature (e.g., 10° C.) in the range of 0 to
30° C. Specifically, the rod-like or fibrous liquid crystalline
gel is prepared by pushing out the gelatin gel in the aqueous solution
containing the chemical crosslinking agent in the container using the
nozzle, in the state where the container in which the aqueous solution
containing the chemical crosslinking agent is retained is placed in the
first incubator. Then, the whole container including the rod-like or
fibrous gel together with the aqueous solution containing the chemical
crosslinking agent is transferred from the first incubator into the
second incubator in which the temperature is kept at 5 to 40° C.,
preferably 10 to 20° C. (e.g., 20° C.) lower than in the
first incubator, and the gelatin solution in the rod-like or fibrous gel
is dialyzed for 1 to 5 minutes. Further, the whole container including
this rod-like or fibrous gel together with the aqueous solution
containing the chemical crosslinking agent is transferred again into the
first incubator, and the gelatin solution in the rod-like or fibrous gel
is dialyzed for 1 to 5 minutes in the first incubator. This way, by
repeating the dialysis of the rod-like or fibrous gel under the
conditions at different temperature, it is possible to form the rod-like
or fibrous liquid crystalline gel having the concentric multilayered
structure when a cross section perpendicular to the longitudinal
direction is observed. By repeating the step of immersing the rod-like or
fibrous liquid crystalline gel in the aqueous solution containing the
chemical crosslinking agent at a predetermined temperature, the step of
taking out the rod-like or fibrous liquid crystalline gel from this
aqueous solution and leaving it stand in air for 5 to 30 minutes and the
step of immersing this rod-like or fibrous liquid crystalline gel in the
above aqueous solution again, the rod-like or fibrous liquid crystalline
gel having the concentric multilayered structure when a cross section
perpendicular to the longitudinal direction is observed may be formed.

[0049]As is the case with the first process, the process in which the
gelatin solution is made into the liquid crystalline gel in the aqueous
solution containing the chemical crosslinking agent to process into a
plate or a film will be described as a representative.

[0050]First the same gelatin solution and aqueous solution containing the
chemical crosslinking agent as in the first process for producing the
liquid crystalline gel are prepared. The gelatin solution is solated at
40° C., this gelatin solution is dropped on a first flat plate,
and a second flat plate having almost the same size as the first plate is
covered thereon to flatten the dropped gelatin solution. The first flat
plate is not particularly limited as long as its surface is smooth and
the formed platy or film-like liquid crystalline gel is easily peeled. As
the first flat plate, glass substrates, plastic substrates and ceramic
substrates are exemplified. The second flat plate is not particularly
limited as long as the plate is smooth and the formed platy or film-like
liquid crystalline gel is easily peeled in order to make the thickness of
the gelatin solution (liquid film) to be flattened even. As the second
flat plate, cover glasses, acrylic plates or PET (polyethylene
terephthalate) are preferable. The size of the second flat plate is not
particularly limited, and its example is selected from the range of the
thickness of 0.12 to 17 mm and the diameter of 15 to 22 mm. The thickness
of the flattened water-soluble polymer solution, i.e., the thickness of
the liquid film is not particularly limited, and if exemplified, the
thickness of 0.5 to 2 mm is preferable. Then, this flattened gelatin
solution sandwiched with the first and second flat plates is placed in
the cold place (4° C.) to gelate for an appropriate time period,
and then immersed in the aqueous solution containing the chemical
crosslinking agent. Even when the gel is immersed in this aqueous
solution, the second flat plate is not peeled from the liquid film by an
interaction with the gelatin solution. In this aqueous solution, the
semipermeable membrane is formed in the part (side circumference of
liquid film), which is not covered with the first and second flat plate
in the flattened gelatin solution (liquid film). This semipermeable
membrane is composed of the gelatin gel induced by the reaction of
glutaraldehyde with gelatin. By keeping this state, the gelatin solution,
which composes the liquid film, is dialyzed, and the platy or film-like
liquid crystalline gel is formed inside the semipermeable membrane. The
thickness of this platy or film-like liquid crystalline gel is
proportional to a radius of the above liquid film and becomes the range
of 0.5 to 2 mm, and the size is proportional to the size of the second
flat plate and becomes a disc having the diameter of 15 to 22 mm. When
the plate surface or the film surface is observed, although not shown in
the figure, the gelatin molecules in the platy or film-like liquid
crystalline gel are in concentric circle and are radially oriented from
the center.

[0051]In order to make the concentric multilayered structure when the
plate surface or the film surface is observed, the following process is
performed. First, the gelatin solution sandwiched with the first and
second flat plates is placed in the cold place (4° C.) to gelate.
Then, the platy or film-like liquid crystalline gel is prepared by
immersing this gelated liquid film in the aqueous solution containing the
chemical crosslinking agent for 10 to 20 minutes to dialyze the gelatin
solution in the liquid film, in the first incubator kept at a
predetermined temperature (e.g., 40° C.) in the range of 10 to
50° C. Specifically, the platy or film-like liquid crystalline gel
is prepared by immersing the gelated liquid film sandwiched with the
first and second flat plates in the aqueous solution containing the
chemical crosslinking agent in the container, in the state where the
container in which the aqueous solution containing the chemical
crosslinking agent is retained is placed in the first incubator. Then,
the whole container including the platy or film-like gel together with
the aqueous solution containing the chemical crosslinking agent is
transferred from the first incubator into the second incubator in which
the temperature is kept at 5 to 40° C., preferably 10 to
20° C. (e.g., 20° C.) lower than in the first incubator,
and the gelatin solution in the platy or film-like gel is dialyzed for 1
to 5 minutes. Further, the whole container including the platy or
film-like gel together with the aqueous solution containing the chemical
crosslinking agent is transferred again into the first incubator, and the
gelatin solution in the platy or film-like gel is dialyzed for 1 to 5
minutes in the first incubator. This way, by repeating the dialysis of
the platy or film-like gel under the conditions at different temperature,
it is possible to form the platy or film-like liquid crystalline gel
having the concentric multilayered structure when the plate surface or
the film surface is observed. By repeating the step of immersing the
platy or film-like liquid crystalline gel in the aqueous solution
containing the chemical crosslinking agent at a predetermined
temperature, the step of taking out the platy or film-like liquid
crystalline gel from this aqueous solution and leaving it stand in air
for 5 to 30 minutes and the step of immersing this platy or film-like
liquid crystalline gel in the above aqueous solution again, the platy or
film-like liquid crystalline gel having the concentric multilayered
structure when the plate surface or the film surface is observed may be
formed.

Examples

[0052]Subsequently, Examples of the present invention will be described in
detail together with Comparative Examples.

Example 1

[0053]A gelatin solution (polymer solution) was prepared by dissolving
gelatin powder at 10 to 30% by weight derived from swine epidermis, which
is one of water-soluble modified proteins, in ultrapure water. This
gelatin solution was dispensed four types (diameter: 6 mm, 16 mm, 20 mm
and 25 mm) of cellulose dialysis tubes, and then each tube is sealed,
left stand in the cold place (4° C.) for 5 minutes, and
subsequently immersed and dialyzed in an aqueous solution of 25% by
weight of glutaraldehyde (aqueous solution containing the chemical
crosslinking agent) at room temperature for 24 hours.

Comparative Example 1

[0054]Until a step of filling the gelatin solution in the dialysis tube,
the manipulation was performed in the same way as in Example 1. The
gelatin solution in the dialysis tube was dialyzed for 24 hours using the
aqueous solution containing bivalent and trivalent metal ions in place of
the aqueous solution containing the chemical crosslinking agent.

<Comparison Test 1 and Evaluation>

[0055]The tubes in Example 1 and Comparative Example 1 were compared. In
Comparative Example 1, the liquid crystalline gel composed of gelatin was
not formed, and when warmed at high temperature, the gelatin solution was
easily solated. On the contrary, in Example 1, the gels having a large
gel strength and four types different diameters were formed in the tube.
At that time, any columnar gels shrank by about 10% compared with the
diameter of the original dialysis tubes. When the gel in Example 1 was
removed from the tube and observed, the gel has the solid-core in the
center part. When these gels were cut in round slices in the direction
perpendicular to the longitudinal direction and observed under crossed
nicols using a polarizing lens, it was identified that the crystal
structure where the molecules were oriented in the longitudinal direction
was present. It was found that the gel tube composed of such a gelatin
liquid crystalline gel could be made irrespective of the size of the
dialysis tube.

Example 2

[0056]A gelatin solution was prepared by dissolving 10% by weight of
gelatin powder derived from swine epidermis, which was one of the
water-soluble proteins, in water. A glass substrate was prepared, the
above gelatin solution was dropped on this glass substrate, and the
droplet was covered with a disc cover glass having a thickness of 0.12 to
0.17 mm and the diameter of 12 mm. This formed a liquid film having the
thickness of about 1 mm between the glass substrate and the cover glass.
Meanwhile, as a solidification liquid containing the chemical
crosslinking agent, the aqueous solution containing 10% ethylene glycol
diglycidyl ether was prepared. The droplet coveted with the cover glass
on the glass substrate was immersed in this ethylene glycol diglycidyl
ether, and dialyzed at room temperature for 24 hours.

Example 3

[0057]The dialysis was performed in the same way as in Example 2, except
that the aqueous solution containing 30% by weight of ethylene glycol
diglycidyl ether was used as the solidification liquid containing the
chemical crosslinking agent.

Example 4

[0058]The dialysis was performed in the same way as in Example 2, except
that the aqueous solution containing 40% by weight of ethylene glycol
diglycidyl ether was used as the solidification liquid containing the
chemical crosslinking agent.

Example 5

[0059]The dialysis was performed in the same way as in Example 2, except
that the aqueous solution containing 50% by weight of ethylene glycol
diglycidyl ether was used as the solidification liquid containing the
chemical crosslinking agent.

Example 6

[0060]The dialysis was performed in the same way as in Example 2, except
that the gelatin concentration was 20% by weight.

Example 7

[0061]The dialysis was performed in the same way as in Example 2, except
that the gelatin concentration was 20% by weight and the aqueous solution
containing 30% by weight of ethylene glycol diglycidyl ether was used as
the solidification liquid containing the chemical crosslinking agent.

Example 8

[0062]The dialysis was performed in the same way as in Example 2, except
that the gelatin concentration was 20% by weight and the aqueous solution
containing 40% by weight of ethylene glycol diglycidyl ether was used as
the solidification liquid containing the chemical crosslinking agent.

Example 9

[0063]The dialysis was performed in the same way as in Example 2, except
that the gelatin concentration was 20% by weight and the aqueous solution
containing 50% by weight of ethylene glycol diglycidyl ether was used as
the solidification liquid containing the chemical crosslinking agent.

Example 10

[0064]The dialysis was performed in the same way as in Example 2, except
that the gelatin concentration was 30% by weight

Example 11

[0065]The dialysis was performed in the same way as in Example 2, except
that the gelatin concentration was 30% by weight and the aqueous solution
containing 30% by weight of ethylene glycol diglycidyl ether was used as
the solidification liquid containing the chemical crosslinking agent.

Example 12

[0066]The dialysis was performed in the same way as in Example 2, except
that the gelatin concentration was 30% by weight and the aqueous solution
containing 40% by weight of ethylene glycol diglycidyl ether was used as
the solidification liquid containing the chemical crosslinking agent.

Example 13

[0067]The dialysis was performed in the same way as in Example 2, except
that the gelatin concentration was 30% by weight and the aqueous solution
containing 50% by weight of ethylene glycol diglycidyl ether was used as
the solidification liquid containing the chemical crosslinking agent.

Comparative Examples 2 to 5

[0068]The dialysis was performed in the same way as in Examples 2 to 5,
except that the gelatin concentration was 0.1% by weight

<Comparison Test 2 and Evaluation>

[0069]After dialyzing in Examples 2 to 13 and Comparative Examples 2 to 5,
the state of the liquid film between the glass substrate and the cover
glass was observed. The results are shown in Table 1.

[0070]As is evident from Table 1, in Comparative Examples 2 to 13, the
liquid film between the glass substrate and the cover glass was not
gelated and remained to be the sol. In Comparative Examples 14 to 17, the
gelatin solution could not keep the liquid film shape, was dissolved and
the liquid crystalline gel was not formed. On the contrary, in Examples 2
to 13, the film was formed in the side of the liquid film between the
glass substrate and the cover glass by the reaction of gelatin with
ethylene glycol diglycidyl ether. This film served as the semipermeable
membrane, and subsequently, a water-insoluble film was formed between the
glass substrate and the cover glass by diffusion of ethylene glycol
diglycidyl ether through the semipermeable membrane. By removing the
cover glass, a disc film having the thickness of 1 mm and the diameter of
12 mm was obtained on the glass substrate. All of the films in Examples 2
to 13 were observed under the crossed nicols using a polarizing plate,
and it was confirmed that all of the films have the crystal structure.

[0071]A myosin solution was prepared by dissolving myosin at 30 mg/mL,
which was the water-soluble protein in the water containing 10 mM
(millimolar) sodium phosphate and 0.6 M potassium chloride salt. This
myosin solution was sandwiched between two cover glasses having the
thickness of 0.12 to 0.17 mm and the diameter of 18 mm to form a liquid
film of the myosin solution. This was immersed in 20 mL of the
solidification liquid (aqueous solution) containing 25% by weight of
glutaraldehyde (chemical crosslinking agent), and dialyzed at room
temperature for 24 hours.

Comparative Example 6

[0072]The dialysis was performed in the same way as in Example 14, except
that the concentration of the potassium chloride salt was 0.12 M.

<Comparison Test 3 and Evaluation>

[0073]After dialyzing in Example 14 and Comparative Example 6, the state
of the liquid film between the two cover glasses was observed. The
results are shown in Table 2.

[0074]As was evident from Table 2, the liquid crystalline gel was formed
in Example 14 whereas no liquid crystalline gel was formed in Comparative
Example 6.

<Comparison Test 4 and Evaluation>

[0075]Changes of a birefringent index Δn by a distance from the
center of the liquid film, which was one of the optical properties, in
the liquid crystal obtained from the liquid crystalline gel in Examples
3, 4, 7, 8, 11 and 12 were measured using a birefringence measurement
apparatus 10 shown in FIG. 5. The results are shown in FIGS. 3 and 4. The
above birefringence measurement apparatus 10 comprises a laser light
emission unit 11 which emits an He--Ne laser light, a photo diode 12
which receives this laser and a photo counter 13 which counts the laser
received by the photo diode 12 as shown in FIG. 5. Between the laser
light emission unit 11 and the photo diode 12, a first lens 21, a first
pinhole plate 31, a sample 14 of the liquid crystalline gel, a second
pinhole plate 32, Berek compensator 16, a polarizing plate 17 and a
second lens 22 are tandemly arranged in this order from the laser light
emission unit 11 toward the photo diode 12.

[0076]From FIGS. 3 and 4, it was found that the gel in the above Example
certainly had an oriented structure. It was also found that the optical
physical property could be optimized for the objective use by controlling
the concentrations of gelatin and the chemical crosslinking agent. From
the above, it becomes possible to make the gel having the oriented
structure and a controlled orientation degree by a simple technique which
is a self-assembly phenomenon without using a microfabrication
technology. By actively using the gel having this controlled orientation
degree gradient, a display instrument having a different advantage from a
display instrument by conventional materials with no gradient, i.e., the
display instrument using the material having the controlled orientation
degree gradient is likely to be developed.

Example 15

[0077]First, the aqueous solution of 10% by weight of DNA was prepared by
dissolving DNA derived from salmon testis in the aqueous solution of 20
mM sodium tetraborate, and the aqueous solution of 10% by weight of
gelatin was prepared by dissolving gelatin derived from swine epidermis
in the aqueous solution of 20 mM sodium tetraborate. The above DNA
aqueous solution and gelatin aqueous solution were mixed in equal amounts
at 40° C. to prepare a mixed aqueous solution containing 5% by
weight of DNA and 5% by weight of gelatin. Then, this mixed aqueous
solution was completely solated at 40° C., this was sandwiched
with two circular cover glasses having the diameter of 12 mm, and then
left stand in a refrigerator at 4° C. for one hour to sufficiently
gelate physically. A thin film of the gel was formed between these cover
glasses. The thin film of the gel was made into the liquid crystalline
gel with the chemical crosslinking agent by immersing this thin film of
the gel in the aqueous solution of 25% by weight of glutaraldehyde and
leaving stand overnight. This liquid crystalline gelation was performed
in the incubator at 10° C. The above thin film of the liquid
crystalline gel was rinsed with the ultrapure water 5 times to remove the
extra crosslinking agent from the thin film of the liquid crystalline
gel. This thin film of the liquid crystalline gel was made Example 15.

Example 16

[0078]The thin film of the liquid crystalline gel in Example 15 was warmed
in the ultrapure water at 40° C. for half a day. This thin film of
the liquid crystalline gel was made Example 16.

Comparative Example 7

[0079]The thin film of the gel was formed between two cover glasses in the
same way as in Example 15. This thin film of the gel was made into the
liquid crystalline gel with the metal cation by immersing the thin film
of the gel in the aqueous solution of 200 mM aluminium chloride which was
the metal salt and leaving stand overnight. This liquid crystalline
gelation was performed in the incubator at 10° C. The above thin
film of the liquid crystalline gel was rinsed with the ultrapure water 5
times to remove the extra metal salt from the thin film of the liquid
crystalline gel. This thin film of the liquid crystalline gel was made
Comparative Example 7.

Comparative Example 8

[0080]The thin film of the liquid crystalline gel in Comparative Example 7
was warmed in the ultrapure water at 40° C. for half a day. This
thin film of the liquid crystalline gel was made Comparative Example 8.

<Comparison Test 5 and Evaluation>

[0081]The thin films of the liquid crystalline gel of the above Examples
15 and 16 and Comparative Examples 7 and 8 were removed from the cover
glasses, put on the slide glass, and a stress and a strain were measured
using a push-fit type elastic modulus measurement apparatus to make a
stress-strain curve. These results are shown in FIGS. 6 to 9.

[0082]As is evident from FIG. 6, it was found that the thin film of the
liquid crystalline gel of Comparative Example 7 in which the liquid
crystalline gel had been made with the metal cation had the higher
elastic modules than the thin film of the liquid crystalline gel of
Example 15 in which the liquid crystalline gel had been made with the
chemical crosslinking agent. In the thin film of the liquid crystalline
gel of Comparative Example 7, the strain was left when the probe was
removed after the measurement, but the thin film of the liquid
crystalline gel of Example 15 was back to the original volume when the
probe was removed after the measurement. From this, it was found that the
thin film of the liquid crystalline gel of Comparative Example 7 in which
the liquid crystalline gel had been made with the metal cation had the
nature that it was hard but the strain was easily left, and that the thin
film of the liquid crystalline gel of Example 15 in which the liquid
crystalline gel had been made with the chemical crosslinking agent had
the nature that it was soft but the strain was hardly left.

[0083]Meanwhile, it was found that in the thin film of the liquid
crystalline gel of Comparative Example 8 obtained by warming at
40° C. the thin film of the liquid crystalline gel gelated with
the metal cation, its volume shrank by about 50%. It was also found that
the thin film of the liquid crystalline gel of Comparative Example 8
became harder than the thin film of the liquid crystalline gel of
Comparative Example 7 before being warmed (FIGS. 7 and 8), and only by
giving a tiny strain, the strain was left. Therefore, it was found that
the thin film of the liquid crystalline gel of Comparative Example 8
became harder by being warmed, and its deformation was easily left.
Meanwhile, it was found that in the thin film of the liquid crystalline
gel of Example 16 obtained by warming at 40° C. the thin film of
the liquid crystalline gel gelated with the chemical crosslinking agent,
its volume shrank by about 20%. In the thin film of the liquid
crystalline gel of Example 16, when a small strain was given, the
relationship between the stress and the strain was scarcely different
from that in the thin film of the liquid crystalline gel of Example 15
before being warmed. However, when the large strain was given, the
relationship between the stress and the strain was different from that in
the thin film of the liquid crystalline gel of Example 15 before being
warmed. A non-linearity appeared and the strain became small (FIGS. 7 and
8). Cracks occurred in the vicinity of the portion to which the strain
was given almost simultaneously when the strain, which caused this
non-linearity, was given. Therefore, it was found that in the warmed thin
film of the liquid crystalline gel of Example 16, although the hardness
of the thin film was scarcely changed, the strain was easily left.

[0084]From the above, it is conceivable that under the condition where the
large deformation is given, it is not desirable to use thin film of the
liquid crystalline gel of Comparative Example 7 gelated with the metal
cation and it is suitable to use the thin film of the liquid crystalline
gel of Example 15 gelated with the chemical crosslinking agent.

Example 17

[0085]First, the aqueous solution of 20% by weight of DNA was prepared by
dissolving the DNA derived from salmon testis in the aqueous solution
containing boric acid and sodium hydroxide (pH=11). The aqueous solution
of 50% by weight of ethylene glycol diglycidyl ether (EGDE) was prepared
by dissolving liquid EGDE in the aqueous solution containing boric acid
and sodium hydroxide (pH=11). Subsequently, the DNA aqueous solution was
filled in the dialysis tube having the diameter of about 8 mm, and this
was dialyzed in the EGDE aqueous solution (chemical crosslinking agent
aqueous solution) kept at 45° C. to make the liquid crystalline
gel. This liquid crystalline gel was made Example 17.

Example 18

[0086]The liquid crystalline gel of Example 17 was immersed in the aqueous
solution at 40° C. for 3 hours. This liquid crystalline gel was
made Example 18.

<Comparison Test 6 and Evaluation>

[0087]The liquid crystalline gel of Example 17 was observed under the
crossed nicols. The result is shown in FIG. 10. As is evident from FIG.
10, it was found that although the liquid crystalline gel of Example 17
was not so fair, the gel was crystallized. It was also found that the
liquid crystalline gel of Example 18 obtained by immersing the liquid
crystalline gel of Example 17 in the aqueous solution at 40° C.
was not dissolved and was gelated, and left the crystal structure when
observed under the crossed nicols. From them, it was found that the
liquid crystal gel of DNA could be prepared by using EGDE, which was the
chemical crosslinking agent. The liquid crystalline gel of Example 17 was
not prepared under the optimal condition, and could not be made into the
so fair liquid crystalline gel. However, it is predicted that the fair
liquid crystalline gel can be prepared by optimizing the parameters such
as a DNA concentration, an EGDE concentration and a reaction temperature.

Example 19

[0088]A gelatin solution containing gelatin was prepared by dissolving 10%
by weight of gelatin powder derived from swine epidermis, which was one
of the water-soluble proteins, in the water. The above gelatin solution
was sandwiched with two disc cover glasses having the thickness of 0.12
to 0.17 mm and the diameter of 12 mm to prepare a thin film of the
gelatin solution having the thickness of 1.5 mm. This thin film of the
gelatin solution was physically gelated by placing it in the cold place
for 10 minutes. Meanwhile, the aqueous solution containing 25%
glutaraldehyde was prepared as the solidification liquid containing the
chemical crosslinking agent, and the above thin film of the gelatin
solution was immersed in this aqueous solution of glutaraldehyde and
dialyzed with keeping the temperature at 10° C. for 24 hours to
make the liquid crystalline gel. The gelatin liquid crystalline gel was
prepared by the above process. This gelatin liquid crystalline gel was
immersed in the ultrapure water at 40° C. to remove unreacted
glutaraldehyde from the liquid crystalline gel. This gelatin liquid
crystalline gel after washing was immersed in 99.8% methanol. This
gelatin liquid crystalline gel was made Example 19.

Example 20

[0089]The gelatin liquid crystalline gel was prepared in the same way as
in Example 19. The gelatin liquid crystalline gel from which unreacted
glutaraldehyde had been removed was immersed in 99.5% ethanol. This
gelatin liquid crystalline gel was made Example 20.

Example 21

[0090]The gelatin liquid crystalline gel was prepared in the same way as
in Example 19. The gelatin liquid crystalline gel from which unreacted
glutaraldehyde had been removed was immersed in 99.5% 2-propanol. This
gelatin liquid crystalline gel was made Example 20.

Comparative Example 9

[0091]The thin film of the gelatin physical gel prepared in Example 19 was
immersed in ethanol. This gelatin physical gel was made Comparative
Example 9.

<Comparison Test 7 and Evaluation>

[0092]Photos obtained by observing Examples 19 to 21 and Comparative
Example 9 under the natural light and under the crossed nicols are shown
in FIG. 11. As is evident from FIG. 11, it is clearly shown that when the
solvent was substituted with alcohol, the gelatin liquid crystalline gels
of Examples 19 to 20 have stronger optical anisotropy than before the
solvent substitution. Meanwhile, in the liquid crystalline gel of
Comparative Example 9, after the solvent substitution, the gelatin gel
became clouded remarkably, and the regular optical anisotropy like in the
gelatin liquid crystalline gels of Examples 19 to 20 could not be
observed. The birefringent indices of the gelatin liquid crystalline gels
of Examples 19 to 20 after the solvent substitution were compared with
those before the solvent substitution. The results are shown in FIG. 12.
As is evident from FIG. 12, it was found that the birefringent index
Δn of the gelatin liquid crystalline gels after the solvent
substitution was enhanced compared with that before the solvent
substitution.

<Comparison Test 8 and Evaluation>

[0093]The Young's modulus of the gelatin liquid crystalline gels of
Examples 19 to 20 after the solvent substitution was compared with those
before the solvent substitution. The results are shown in FIG. 13. As is
evident from FIG. 12, it was found that the value of the Young's modulus
of the gelatin liquid crystalline gels after the solvent substitution was
larger than that before the solvent substitution.

[0094]From the results of the above comparison test and evaluation, it was
found that the birefringent index and the Young's modulus of the liquid
crystalline gel obtained by using the chemical crosslinking agent could
be controlled by substituting the swelling solvent with another solvent.
Such a control of the physical property by a post-treatment of the liquid
crystalline gel is the technology, which was impossible in the liquid
crystalline gel obtained by using the metal ion.

Example 22

[0095]A gelatin solution containing gelatin was prepared by dissolving 20%
by weight of gelatin powder derived from swine epidermis, which was one
of the water-soluble proteins, in the water. The above gelatin solution
was sandwiched with two disc cover glasses having the thickness of 0.12
to 0.17 mm and the diameter of 12 mm to prepare a thin film of the
gelatin solution having the thickness of 1.5 mm. This thin film of the
gelatin solution was physically gelated by placing it in the cold place
for 10 minutes. This thin film of the gelatin solution was immersed and
dialyzed for 20 minutes in the aqueous solution of 25% glutaraldehyde in
the incubator kept at 10° C. Then, the above sample was
transferred to the incubator at 40° C. Subsequently when the thin
film of the gelatin gel was immersed and dialyzed in the aqueous solution
of glutaraldehyde, the temperature was changed alternately e.g.,
10° C., 40° C., 10° C. and 40° C.

Comparative Example 10

[0096]A liquid crystalline gel was obtained in the same way as in Example
22, except that the temperature at which the thin film of the gelatin gel
was immersed and dialyzed in the aqueous solution of glutaraldehyde was
kept at 10° C. and was not changed.

<Comparison Test 9 and Evaluation>

[0097]Photos obtained by observing the gelatin gels prepared in Example 22
and Comparative Example 10 under the crossed nicols were shown in FIG.
14. The gelatin liquid crystalline gel prepared in Comparative Example 10
had only two layers whereas the gelatin liquid crystalline gel prepared
in Example 22 had the multilayer structure.

INDUSTRIAL APPLICABILITY

[0098]The liquid crystalline gel applied by the present applicant and
prepared by dialysis or immersion in the aqueous solution of the metal
cation is formed by the physical bond between the ion and the polymer. On
the contrary, the liquid crystalline gel provided by the present
invention is formed by the covalent bond between the chemical
crosslinking agent and the polymer. This is a novel point. Therefore, it
became possible to prepare the various liquid crystalline gels by
designing the combination of the appropriate polymer with the chemical
crosslinking agent. For example, it is possible to easily produce the
display instrument having the birefringence gradient by forming a main
chain type liquid crystal polymer using the process for producing the
liquid crystalline gel of the present invention.

Patent applications by Kazuya Furusawa, Gunma JP

Patent applications by Takao Yamamoto, Gunma JP

Patent applications by Toshiaki Dobashi, Tochigi JP

Patent applications by NATIONAL UNIVERSITY CORPORATION GUNMA UNIVERSITY